A ubiquitous network technology has been captured the world's attention. The ubiquitous network technology allows a user to access various networks regardless of time and location. Such a ubiquitous network technology includes a radio frequency identification (RFID) technology or a ubiquitous sensor network (USN) technology, and a system employing these technologies is called an RFID/USN system.
The ubiquitous sensor network (USN) technology is referred to as a network technology of constructing a network such that plural pieces of information collected by various sensor are obtained in wireless. According to the USN technology, a plurality of sensor network nodes are installed in a region where the access of a person is difficult, thereby allowing the person to monitor the region.
An RFID system for commercial transaction includes an RFID tag attached to goods and equipped with detailed information about the goods and an RFID reader for reading the detailed information embedded in the RFID tag through RF communication. The RFID tag attached to the goods transmits the information to the RFID reader through RF communication while passing through an area where the RFID reader is positioned. Accordingly, there is provided an infrastructure capable of effectively processing supply chain management (SCM) including the distribution, the assembly, the price change, and the sale of goods.
When the RFID reader transmits an information requesting signal, the RFID tag transmits the tag information according to the signal. At this time, a signal transmitted from the RFID tag, which is located beyond the reading distance of the RFID reader, may not arrive at the RFID reader, but leaked.
In the RFID/USN system, if the signal provided from the RFID tag is leaked, the RFID reader cannot generate exact information about physical distribution. Thus, the RFID/USN system must be provided with more many RFID readers in order to solve the above problem. However, if the number of the RFID readers increases, radio interference is strongly caused between the RF readers, so that a tag recognition rate and a tag recognition distance may be reduced. In addition, the complex network may be required.